7,432 research outputs found

    Noncompact Gauge-Invariant Simulations of U(1), SU(2), and SU(3)

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    We have applied a new gauge-invariant, noncompact, Monte Carlo method to simulate the U(1)U(1), SU(2)SU(2), and SU(3)SU(3) gauge theories on 848^4 and 12412^4 lattices. The Creutz ratios of the Wilson loops agree with the exact results for U(1)U(1) for β≥0.5\beta \ge 0.5 apart from a renormalization of the charge. The SU(2)SU(2) and SU(3)SU(3) Creutz ratios robustly display quark confinement at β=0.5\beta = 0.5 and β=2\beta = 2, respectively. At much weaker coupling, the SU(2)SU(2) and SU(3)SU(3) Creutz ratios agree with perturbation theory after a renormalization of the coupling constant. For SU(3)SU(3) the scaling window is near β=2 \beta = 2 , and the relation between the string tension σ\sigma and our lattice QCD parameter ΛL \Lambda_L is σ≈5ΛL\sqrt{\sigma} \approx 5 \Lambda_L.Comment: For U(1), we switched from beta = 2 / g^2 to beta = 1 / g^2; 3 pages; latex and espcrc2.sty; one figure generated by PiCTeX; our contribution to Lattice '9

    Decision rules and information provision: monitoring versus manipulation

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    The paper focuses on the organization of institutions designed to resolve disputes between two parties, when some information is not veri…able and decision makers may have vested preferences. It shows that the choice of how much discretional power to grant to the decision maker and who provides the information are intrinsically related. Direct involvement of the interested parties in the supply of information enhances monitoring over the decision maker, although at the cost of higher manipulation. Thus, it is desirable when the decision maker is granted high discretion. On the contrary, when the decision maker has limited discretional power, information provision is better assigned to an agent with no direct stake. The analysis helps to rationalize some organizational arrangements that are commonly observed in the context of judicial and antitrust decision-makin

    Broad Line Radio Galaxies: Jet Contribution to the nuclear X-Ray Continuum

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    It is shown that, for Broad Line Radio Galaxies the strength of the non-thermal beamed radiation, when present, is always smaller than the accretion flow by a factor < 0.7 in the 2-10 keV band. The result has been obtained using the procedure adopted for disentangling the Flat Spectrum Radio Quasar 3C 273 (Grandi & Palumbo 2004). Although this implies a significantly smaller non-thermal flux in Radio Galaxies when compared to Blazars, the jet component, if present, could be important at very high energies and thus easily detectable with GLAST.Comment: 12 pages including 2 figures (4 files), ApJ accepte

    Relativistic Jets from X-ray binaries

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    In this review I summarise the status of observational research into relativistic jets from X-ray binaries, highlighting four areas in particular: (i) How relativistic are the jets ?, (ii) The disc : jet coupling, (iii) the nature of the underlying flat spectral component, and (iv) the relation between jets from black holes and those from neutron stars. I have attempted to discuss the extent of our (limited) physical understanding, and to point the way towards relevant new observational tests of the various phenomena.Comment: Review article, to be published in `Astrophysics and Cosmology : A collection of critical thoughts', Springer Lecture Notes in Physic

    Jets and outflows in Radio Galaxies: implications for AGN feedback

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    One of the main debated astrophysical problems is the role of the AGN feedback in galaxy formation. It is known that massive black holes have a profound effect on the formation and evolution of galaxies, but how black holes and galaxies communicate is still an unsolved problem. For Radio Galaxies, feedback studies have mainly focused on jet/cavity systems in the most massive and X-ray luminous galaxy clusters. The recent high-resolution detection of warm absorbers in some Broad Line Radio Galaxies allow us to investigate the interplay between the nuclear engine and the surrounding medium from a different perspective. We report on the detection of warm absorbers in two Broad Line Radio Galaxies, 3C 382 and 3C 390.3, and discuss the physical and energetic properties of the absorbing gas. Finally, we attempt a comparison between radio-loud and radio-quiet outflows.Comment: To be published in the proceedings of High Energy Phenomena in Relativistic Outflows III (HEPRO III, IJMPCS). 4 pages, 2 figure
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